The arrests of four Iranians for alleged involvement in a U.S.-financed plot to topple Tehran's Islamic government come amid fresh U.S. media reports that President George W. Bush has authorized a major program for covert operations in Iran.

According to those reports, the Bush administration has been sponsoring a campaign of "subtle sabotage" to undermine Tehran's controversial nuclear program -- which Washington alleges is aimed at building nuclear weapons.

James Denselow, a security expert at King's College in London, says such operations constitute a secret proxy war between the United States and Iran.

"The Americans have been playing Iran at its own game," Denselow tells RFE/RL. "Iran has been sponsoring anti-U.S. groups in Iraq since the 2003 invasion. As late ago as 2005, the U.S. has been sponsoring anti-Iranian groups in Iran -- particularly in the southern provinces on the eastern side where a population that is not homogeneous or acquiescent to the rule in Tehran is able to be co-opted with money and with weapons."

"This is very much a secret war," Denselow said. "But it puts pressure on Iran just as Iran has been putting pressure on the United States in Iraq."

Indeed, authorities in Tehran have alleged for years that Washington has been financing sabotage operations in Iran.

David Sanger, the chief Washington correspondent for "The New York Times," says he learned details about such operations while conducting interviews with senior U.S. officials for his new book, "The Inheritance," which was released this month.

Sanger's book focuses on the challenges that Barack Obama will inherit from the Bush administration when he is inaugurated on January 20. Iran is seen as one of Obama's key challenges.

Speaking on the U.S. television program "Meet The Press," Sanger said Obama ultimately will have to decide whether to allow such covert U.S. operations to continue.

"We are beyond the point of saying that Barack Obama inherits a lot of messes around the world," Sanger said. "He also inherits a lot of activities that President Bush began. And he is going to have to make some very difficult decisions about whether to continue them."

"There are covert actions that have begun that Obama is going to have to look at even before he fully understands them," Sanger said. "One of Obama's aides said to me, 'You know, in many ways, we have a "Bay Of Pigs" problem,' which is the action [in Cuba] that President Kennedy inherited from Dwight Eisenhower. And [Eisenhower] didn't fully understand it."

Behind The Scenes

Sanger says Bush stopped Israel from carrying out air strikes on Iran's nuclear infrastructure last year by telling Israeli officials that ongoing U.S. covert operations in Iran would be more effective.

He says U.S. Secretary of Defense Robert Gates convinced Bush that an attack on Iran's nuclear facilities would probably be ineffective -- leading to the expulsion of international nuclear inspectors and causing Iran to be even more secretive about its uranium-enrichment program.

Sanger has reported that Bush denied an Israeli request to fly its warplanes through Iraqi airspace in order to attack the nuclear complex at Natanz -- Iran's only known uranium-enrichment plant. He says Bush also refused a request by Israel last year for powerful bunker-piercing bombs needed to attack the underground nuclear complex.

Israel's attempts to obtain bombs and permission to fly over Iraq appears to have grown out of its concerns about a U.S. National Intelligence Estimate in 2007 that suggested Iran had effectively suspended development of a nuclear warhead in 2004.

Mike McConnell, director of U.S. National Intelligence, says he regrets that the publicly released portions of the National Intelligence Estimate emphasized only the changes in Iran's nuclear work rather than a broader overview.

Speaking recently on the interview program "Charlie Rose," McConnell said the National Intelligence Estimate was misinterpreted as saying that Iran was not trying to develop nuclear weapons. In fact, McConnell says, the report refutes Iran's claims that it has never tried to build nuclear weapons.

McConnell noted that Iran continues to develop missiles capable of carrying a nuclear warhead into Israeli territory, and that it continues to enrich uranium needed to build nuclear weapons.

Investigative journalist Seymour Hersh quotes numerous sources as saying that the U.S. Congress agreed to a Bush request in late 2007 to fund an escalation of covert operation in Iran. Hersh says those operations began as early as 2005.

"The president signed a series of executive orders and findings [in late 2004] permitting the Pentagon to run clandestine, covert operations -- operations which Americans go into countries under cover. American commandos, run by the Pentagon. The CIA no longer is the sole agency doing these kinds of missions. And I'll tell you why that is very important," Hersh says. "Under the law as it now stands, the CIA when it runs a covert operation, the president has to approve. He has to sign a finding -- a formal paper saying, 'I know about it. And here, Congress, is what's going on.'"

But unlike covert CIA operations, Hersh says, the Bush administration's interpretation of the law is that Congress does not need to be informed about clandestine military operations controlled from the Pentagon. That means U.S. lawmakers have only been partially informed about how the money they appropriate is being used in joint operations by the Pentagon and CIA.

Talk Of Talks

In a shift from Bush's policy approach, Obama has pledged to increase diplomatic efforts on Iran and talk directly to its leaders. While it is not yet clear whether Obama will allow U.S. covert operations to continue in Iran, he has spoken about the need to provide resources and guidance for those who carry out U.S. intelligence missions:

"Here in Washington, we have also learned some tough lessons. We have learned that to make pragmatic policy choices, we must insist on assessments grounded solely in the facts, and not seek information to suit any ideological agenda," Obama says. "To support those who carry out our intelligence mission, we must give them the resources they need and the clear guidance they deserve. And we know that to be truly secure, we must adhere to our values as vigilantly as we protect our safety - with no exceptions."

Iranian Foreign Ministry spokesman Hassan Qashqavi says Iran ultimately will undertake what he called "appropriate, timely, and proportionate measures" to any new approaches by the United States after Obama is inaugurated:

"Many times, we've said that we will see in what form this change will take place," Qashqavi says. "Is it a fundamental change in the behavior and stance of the United States in relation to the Islamic Republic of Iran, or not?"

Denselow, the security expert at King's College in London, concludes that Obama is unlikely to put an immediate end to ongoing covert operations in Iran:

"The Iran policy that Obama picks up will have to be one of carrots and sticks and normal diplomacy," Denselow says. "He will have to chose whether to use [those covert operations] as a means of putting pressure on Iran or to stop it as a mans of alleviating that pressure to try to foster greater relations. There is a lot of questions to be answered relating to Iran's nuclear program and its relationship with Israel. And I think Obama will be careful about not giving away all his cards onto the table. The proxy war in southern Iran is, after all, simply another pressure point that the Americans can use to play hardball with Iran. It certainly is a lot more subtle than full-on airstrikes or an Israeli attack."